What is Via in PCB design? Everything you need to know about it!

By | Date posted: | Last updated: April 5, 2022
Via in PCB design

With the growth of miniaturization in appliances, PCBs continue to become smaller and use fewer through-hole components. With space being constrained, surface mount technology becomes increasingly popular and the majority of through holes on most modern PCB designs end up being vias.

What is a via?

Essentially a via offers a conductive path for the electric signal to go from one circuit layer to another. A via is a plated through hole in a PCB that can be used to route a trace from the board’s surface to the inner and outer layers. Vias are essential in multilayer boards as they create the routes for flow of current between the various layers.

Types of PCB Vias

While vias perform the same broad function, there are different types of vias as well as different options for the final appearance of the vias on the PCB surface.

PCB Via Structures – Through, Blind, Buried

Through Vias

This is a hole that is drilled from the top to the bottom layer. It is open at both ends to allow for plating solution to flow through. In fact, through vias are the commonest and most used. All you need to do is to follow the fabricator’s rules for minimum diameter, maximum aspect ratio and adjacency.

Blind Vias

Mechanically drilled blind vias are drilled from the top or the bottom layer but do not travel the full distance through the PCB. Unlike a through via, a blind via is open only at one end, so the plating solution cannot flow all the way through the hole. In going for blind vias, it is best to go with large holes, small aspect rations and aggressive plating agitation so that air bubbles aren’t trapped at the bottom of the holes.

Buried Vias

These are used to connect internal layer structures. Sometimes they connect only internal layer pairs before being laminated.

Laser microvias

These are the smallest vias, usually around 0.003″ – 0.004″ in diameter. The big advantage with microvias is that they can fit onto tight land areas often as vias-in-pads. The pads are planarized to their original condition after plating. The pad surfaces are restored so that they can be used for component soldering. With laser microvias, the maximum aspect ratio is usually 1:1. It is therefore practical to connect 2 adjacent layers with a thin dielectric sheet. If the design is extremely dense, they can be stacked one over the other.

How are PCB vias covered or filled?

Very often additional treatment is required for the vias to improve performance and yield. Some of these methods include:

  • Epoxy Hole Filling
  • Secondary Solder Masking

These additional processes eliminate assembly issues that can lead to costly troubleshooting & rework.

In fact, an appropriate via treatment can help mitigate many of these issues. Let us look at some of them in detail:

Tented Vias

These vias have a non-conductive solder mask that covers the pad at both ends. Tenting via in PCB fabrication became popular when dry film solder mask was greatly used, and it could tent even relatively large holes. Today, the use of dry film masks is extremely limited. The old form of tenting, therefore, is impractical.

Encroached Vias

These have a solder mask over most of the pad but end before the hole by a few thousandths of an inch. The solder mask increases the distance between the via and the solderable pad. Also with the hole being open, there is no likelihood of any air pocket formation or contaminant entrapment.

Button Print & Plugged Vias

Essentially these are variations of filled vias. They go a long way in helping with solder flow-through. It ensures that during assembly you have the correct amount of solder on the pad. It is recommended that the PCB material used for these processes is a non-conductive epoxy hole fill. The vias need to be limited to 0.020” maximum diameter so that the hole is filled effectively.

Active Pads

They plug the hole as well as the plates over the plug. Also known as via-in-pad, it is required where the pad through which the via was originally drilled is to be used later for soldering the surface mounted component. It is also useful where you need to cool a hot-running component by drawing heat through the via. With heat drawn to the opposite side of the board, it can dissipate easily.

It is important to know that via-in-pad hosts small pitch sizes and minimizes your board’s general size. This technique works well for BGA footprint parts.

How to figure out the correct via requirements for your PCB?

The kind of via that you choose has a lot to do with the size and the functionality of your board. For example, if the board is to be used in a large computing device, the PCB design will need to conform to older standards. Possibly, a PCB with through-hole components will work best in such a situation. A PCB, for a smaller device, on the other hand, will not benefit from through hole components. In this case, you will need to make the best use of the small amount of space available. In small boards, therefore, blind micro vias will work best. Such blind micro vias can send strong signals between short distances. While small PCBs with micro vias will entail a high investment especially in terms of labor costs, however the investment will well be worth it, especially since the path breaking device could turn out to be a bestseller.

How to state your PCB via requirements?

It is imperative that your via requirements be stated clearly in the fabrication documentation. In fact, separate files for each set of vias used in the design are highly recommended. In addition, the following information needs to be provided to the fabricator:

  • Type of Via- Is it through, blind or buried?
  • What is the via diameter?
  • The tolerances
  • Layer pairs to be connected by each drill file, if blind or buried.

In terms of treatment too, you need to give the fabricator the specific details such as whether you want the plug vias partially or 100% filled. Information such as using non-conductive epoxy, applying surface finishing over the pad and more, should be painstakingly detailed. In fact, the more specific you are the better results you will get. If on the other hand, there is lack of clarity in your fabrication notes, you could face issues such as:

  • Delay in receiving quotes.
  • Impact on bare PCB delivery.
  • Complication in the assembly cycle.

In fact, with miniaturization of appliances and the prevalence of high-density designs, it is becoming exceedingly important to clearly detail the via type as well as the treatment you require. It is also important to check that your data files are accurate and match with the requirements. In fact, time that is spent on detailing the requirements correctly will go a long way in ensuring there are no costly errors at a later date.

To sum up

Vias are becoming increasingly important on account of the following:

  • In multi layered boards they help with establishing component density.
  • They raise trace density in multi-layered PCBs. They allow various traces to link with each other. In such cases they act as vertical connection factors.
  • They help in facilitating the transmission of signals between layers. Without the use of vias the PCB components need to be routed on a single plane.

We have more than 4 decades of experience in PCB manufacturing in USA. At Technotronix, we have the technology and production facility to offer the tenting of PCB vias with the highest degree of accuracy. With our experienced engineers you can rest assured that what you will get is an effective production. Our ability to deliver, unparalleled quality as well as customer service, is what makes us stand out. Both on-time delivery and price competitive products are our USP. The most important element of our success, however, has been the relationships we have developed with our customers.

In case you have any questions, please feel free to contact us via email at [email protected] or call us on 714/630-9200.

The Top Difference between PCB Core and Prepreg Materials!

By | Date posted: | Last updated: March 23, 2022
difference-between-pcb-core-and-prepreg

To understand the difference between PCB core & prepreg material, it is important to understand what each of these are:

What is prepreg material?

Simply put, prepreg is a conductive substance that is used to offer the appropriate insulation between the copper and the core of the PCB. It is a dielectric material that is sandwiched between two cores of between a core and a copper foil. It is often referred to as the binding material as it binds two cores or a core and a copper foil.

As its name indicates, prepreg is a glass fiber impregnated with a resin bonding agent. All prepegs are B-stage materials. There are different types of prepregs depending on their thickness and the resin content that they hold. Prepregs are broadly available in 3 formats depending on their resin content:

  • Standard Resin
  • Medium Resin
  • High Resin

A typical prepreg preparation process involves:

  • Reinforcing with resins
  • Removal of excess resins
  • Preparation of curing with high and low-temperature settings

Why is it important?

Prepreg is an essential component of the PCB manufacturing process on account of the following:

  • It is easy to apply and work with. It is easy to getting accustomed to and does not require too much technical expertise.
  • It is not messy as opposed to wet style layups. The waste management during the manufacturing process is therefore, efficient.
  • There is a wide variety of prepreg available to suit different requirements.
  • It helps in reducing the weight of the device and therefore is particularly helpful in a milieu where miniaturization of devices has become a norm.

What is PCB core material?

The core of the PCB is a rigid base material, which is laminated with copper. It is used in manufacturing single or double-sided boards as also multilayer PCBs. A multilayer PCB has the following components:

  • Copper foil
  • Prepreg materials
  • Copper foil
  • Core materials
  • Copper foil
  • Prepreg materials
  • Copper foil

The difference between PCB core vs prepreg:

Oftentimes on account of the similarity between prepreg and core, there is a confusion between the two. Simply put, the core is a product of the prepreg and lamination. It is therefore far more rigid compared to the prepreg. The core is made up of a fiberglass-epoxy laminate which is Flame Retardant and has copper on either side.

The prepreg, on the other hand is partially dried without lamination and isn’t as rigid as the core.

Another important difference between the PCB prepreg and the core is its dielectric constant. While the dielectric constant of the core does not vary, that of the prepeg varies before & after lamination. The different dielectric constants are also a function of the following:

  • Resin content
  • Type of resin
  • Glass weave

This can become an issue where you need precise impedance matching. Also with not all prepreg and core materials being compatible with each other, and core/prepreg stacks with different doelectric constants, it is hard to predict the exact dielectric constants as well as losses in an interconnect.

The thickness of the PCB is a function of the prepregs used. In fact the required thickness can be achieved by a combination of prepreg plies i.e thin sheets of prepregs placed one over the other.

At high voltage, irrespective of the PCB core or prepreg material used, creepage as well as leakage currents are an issue. Creepage specifications for FR4 materials are required for electromigration of copper and growth of conductive filaments. On account of this issue and also with a view to increase glass transition as well as decomposition temperatures, there has been a move towards non-dicyandiamide resins.

To Sum Up

Both the core and the prepreg are essential components of the PCB. While the core is a base PCB material, a multilayer PCB is held together by the prepreg. The difference between the two lies in the fact that the core is cured, while prepreg materials are malleable which means it can be easily formed into sheets. When subject to high temperatures the material melts, helping to fuse the layers.

With over 40 years of combined experience in rendering high quality and standard PCB assembly and manufacturing services, we are not just an assembler, we can completely test at board level to box build level to provide the benefit of unparalleled technical expertise and the most progressive solutions at competitive prices. At Technotronix, we have adopted advanced PCB production techniques & manufacturing practices with specialization in a varied range of PCB fabrication processes, producing high-quality multi-layered PCBs from tailor-made layouts

In case you have any questions, please feel free to contact us via email at [email protected] or call us on 714/630-9200.

The most common myths & facts about PCB board design!

By | Date posted: | Last updated: March 15, 2022
pcb-board-design

While PCB board design plays an extremely important role, the fact also remains that there are several myths associated with printed circuit board design. Holding on to these misconceptions can lead not just to higher overall production costs but also defective boards. It will be worthwhile to look at some common myths about PCB board design.

Here is a list of the most common misconceptions about PCB board design that need to be debunked:

Design Rules are common for rigid and flexible circuits board

Far from it! There are a number of things that need to be kept in mind depending upon whether you are designing for a rigid or a flexible circuit. Some of the things to be kept in mind include:

  • Flexible circuits need to take into account locational stresses as they need to be folded and bent
  • The design also needs to pay heed to the dimensional stability of the base materials

Component placement does not make a difference

Contrary to popular thinking, circuit performance has a lot to do with careful placement of parts. Placing parts just about anywhere on the board or even grouping similar parts together to save space, does not work. You need to consider a wide variety of factors including but not limited to heat and electrical overload. You also need to consider the height, width and size of components. Every component needs to sit in the right location. Quality PCB assembly also needs to make sure that the PCB doesn’t overheat and isn’t too high on power consumption.

The use of via in pad is not conducive to the circuit board

You certainly need to be careful when using via in pad as plating chemicals can get trapped if you don’t cap or mask it. However, that does not mean that the via in pad should be totally avoided. In fact via in pad have a number of uses, including but not limited to:

  • They work well when you need to place close bypass caps
  • They help in thermal management and grounding
  • They assist in pitch BGA routing

90 degree angles are to be avoided

This is true only when PCBs were etched with acid as the sharp corners would mean acid would collect there. With etching now being done with alkaline, acid traps aren’t an issue any more. 90 degree angles therefore are no longer to be avoided.

Design is all

While it is natural to want your design to be as elegant as possible, the fact remains that other than the design you need to take into account a wide variety of factors. These include:

  • The material available
  • The tools used, and more

While on paper you can have any track width, spacing, annular rig size and more, the final product needs to take into account the real world limitations. A lovely design on paper may not therefore turn out to be effective in the real world. The design, therefore, needs to take into account real world limitations. If this is done correctly, you will not have costly mistakes to contend with at a later date that will cost you time and money and impact your go-to-market.

The design software is inconsequential

The normal tendency is to go with a PCB design software that comes cheap. Nothing wrong there as cost-effectiveness of the software impacts your total project cost. However, choosing the right PCB board design software involves a number of factors other than cost alone. Some of these factors include:

  • Type, quality and quantity of content
  • Availability of community support
  • Integration of supply chain
  • MCAD integration
  • Management of library components, and more

In fact you need to closely evaluate issues like the kind of user interface required, the kind of pricing and more to come to a balanced decision.

With these myths debunked, it is that much easier to pay due attention to aspects that will add to efficiency of design of your PCBs. What this in turn means is the rise of new innovations and a general betterment in the quality of life.

We have over 4 decades of experience in providing innovative high-speed PCB design & manufacturing services. We take an extra step to reach out to your exact PCB manufacturing requirements, high-quality standards, and a strong customer support service to provide quick turnarounds & on-time delivery to our customers. Submit your any custom PCB board design service requirements via PCB design quote form along with BOM (Bill of Material) and Gerber files and we will get back to you soon. Alternatively, you can email your requirements at [email protected] or call us at 714/630-9200.

PCB Mouse Bites vs V-Grooves: What is the difference?

By | Date posted: | Last updated: March 8, 2022
pcb-mouse-bites-vs-v-grooves

Before we look at the difference between PCB Mouse Bites & V-Grooves, it will be worthwhile to begin with looking at what exactly is PCB panelization and what are the various factors to consider in choosing the right technique from amongst the several available.

What is PCB Panelization?

Essentially PCB Panelization allows you to connect smaller circuit boards into a large array. The vendor performing panelization can equally easily depanelize the array. In fact, depanelization is known to increase throughput of PCB.

Factors to Consider for PCB Panelization

The choice of the panelization method depends on a wide variety of factors. Some of these include:

  • Design – Aspects such as clearance between the board’s edge and its components, the presence of edge-hanging components can impact the choice of panelization
  • Components- If the board has sensitive connectors and components, the choice of panelization techniques will be impacted.
  • Materials – The type of PCB material used also determines the panelization technique. For example, some materials are prone to splintering. Similarly, if the boards are very thick you could face issues.
  • Shape – The shape of the printed circuit board also impacts panelization.

PCB Panelization Methods

The broad methods of PCB Panelization include:

  • V-Groove Panelization
  • Tab Routing Panelization
  • Performated Tab Routing or what is known as Mouse Bites

Let us look at PCB Mouse Bites versus V-Groove in some detail:

What is perforated tab routing or mouse bites?

This technique involves drilling small, perforated holes in tabs. It is in their similarity to mouse bites that this technique gets its name. The manufacturer pre-cuts the boards on the array and holds them in place with the perforated tabs.

This method works well where:

  • The components aren’t too heavy
  • It supports edge-hanging component designs which is a source of significant advantage.

The advantages of Perforated tab routing Or Mouse Bites include:

  • They offer a good grip when mounted
  • They work well if you want to use hand separation as a technique of separation.

With perforated tab routing, the areas of concern, however, remain as below:

  • It leaves material on edges. It therefore necessitates sanding. In turn, this not only involves a cost but also consumes time.
  • For holes more than 0.6 inches, a placeholder or knockout might be needed
  • There is a chance of these popping out earlier than needed.

V-Grooves

Also known as V-scoring, v-groove panelization involves separating individual boards housing V-shaped grooves. With this method, the manufacturer can remove 1/3 of the thickness of the board from the top and the bottom. They need to be cut with the help of a machine typically at an angle of 30 or 45 degrees. This method does not lend itself to hand separation as it can put stress on the board as well as its surrounding components.

In this method, the panelization has to have a 0.05 inch clearance from the components to the groove’s center.

V-Groove panelization works well for square and rectangular shaped board. You, however, cannot use it to cut straight lines through the array.

Essentially, this method works well where:

  • There are no overhanging components
  • There are no round corners
  • Where there is a sufficient distance between the component limit and edge of the PCB.

The other advantages of V-Groove include:

  • It is more cost-efficient than mouse bites
  • V-scores are easier to make
  • They offer greater strength

The concerns with depanelizing V-scored PCBs include:

  • It needs a lot of force to break apart and hence requires dexterity to see that components are not harmed during the process
  • In case the copper traces are too close to the score, it can result in splitting.

To Sum Up:

PCB panelization has emerged as an important step when it comes to PCB manufacturing and assembly. By knowing the benefits and constraints of each of the methods outlined above, you can ensure that you do not make any costly mistakes. Also, by knowing the strengths and weaknesses of each technique, redesigns and delays can be avoided, significantly impacting your go-to-market and giving you the much-needed competitive edge.

Technotronix is one of the leading PCB manufacturers based in the USA. We have over 4 decades of experience in providing innovative PCB manufacturing services using modern technologies and the latest machinery. We are adhering to strict high-quality standards and compliant with the RoHS quality management system.

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